Traditional tissue closure devices such as staples, sutures, adhesives, etc. while useful, may not be best suited for every indication. For example, a tissue closure system that eliminates the need for any implant (such as an anchor, suture, clip, etc.) may be well suited for minimally invasive tissue closure and/or may decrease patient recovery time. The term tissue closure may comprise sealing, melding, or otherwise fastening together various tissue and/or closing an opening in tissue after the creation of an opening. To accomplish tissue closure, the devices and methods minimally damage the tissue (e.g., by the application of energy) producing a healing response that generates collagen. To assist in tissue closure, the methods and devices may also apply compression to the tissue(s) to be sealed. Heating the tissue causes various factors to be secreted by the tissue, including factors such as tissue necrosis factor beta, tissue plasminogen activator, and others that result in migration of fibrocytes that secrete collagen.
The following two examples of tissue closure illustrate situations highlighting the need for tissue closure devices. However, it is understood that the invention described herein may also have a broad range of applicability beyond the illustrated examples.
One instance requiring tissue closure systems results from incomplete development of a body organ or pathway. Many circumstances occur in nature, and particularly in mammals, involving incomplete development of the embryo and early infant. One such circumstance occurs during the conversion from intrauterine circulation without lungs, to extrauterine circulation dependant on lung gas transfer.
During intrauterine circulation, a fetus does not use it's own lungs to oxygenate the blood. Instead, the mother's placenta supplies the fetus with oxygenated blood through the umbilical cord. Therefore, during intrauterine circulation, it is not necessary for the blood to travel from the fetus' heart to its lungs and then back to its heart. As shown in FIG. 1, a small opening in the atrial septum 2 comprises adjacent flaps of tissue 4 and 6. This opening, the foramen ovate, allows the blood (as shown by arrow A) to skip the fetus' lungs and travel from the veins to the right side 3′ of the fetus' heart directly to the left side 3′″ of the heart. The foramen ovate generally consists of two flaps of the atrial wall. Normally, during the conversion to extrauterine circulation at birth, the foramen ovale closes as a result of blood pressure on the left side of the heart and subsequent healing between the two flaps. This appears to be, in part, dependant on prostaglandins and other tissue factors. The condition where the forum ovate fails to close is called patent forum ovale (PFO).
Natural pathways such as the ductus arteriosus and foramen ovale, normally close after birth. In some circumstances, however, these pathways remain patent or partially open, and the PFO allows improper blood flow or foreign material, such as blood clots, to move into the bodily circulation. This condition may result in strokes, heart attacks, or can change the pressure and volume of blood going to the brain and other organs, perhaps causing migraine headaches. It is beneficial to close these pathways, but conventional procedures involve major surgery to open the chest and heart while the patient requires artificial circulation on a heart-lung bypass machine. Some procedures have attempted placement of artificial appliances/devices through the patent foramen ovale in an attempt to keep both loose flaps from separating without actually melding them together.
Another example requiring tissue closure involves closure of blood vessels. Access to the circulation for procedures such as angioplasty and/or stent placement into the coronary arteries often involve arterial puncture sites. Conventionally, closure of these arterial access sites involves sutures or thrombogenic sponges, or similar foreign objects. However, these solutions require that the patient remain immobile while the natural clotting and healing process occurs at the puncture site.